LilacServer is a Web developed in Java that employs Java NIO technology. It is fast and highly productive. It is also a template engine with its own language for creating templates and a framework with its own API.
More features of interest: built-in support for databases via JDBC; integrated localization facilities; sophisticated caching capabilities; support of sessions, multi-part forms, and file uploads; support of third-party libraries; a Web-based management interface; and so on.

Collax Business Server is an all-in-one Linux server for small- and medium-sized businesses. It delivers all the important network services within a heterogeneous business environment for communication, infrastructure, compliance, groupware, and storage, all in a reliable and secure way which is easy to manage. It also provides essential security functions such as firewalling and virus and spam filtering, to protect against hacker attacks, viruses, and unsolicited email messages.

NXWEB is ultra-fast and super-lightweight web server for applications written in C. It can serve thousands of concurrent requests with a small memory footprint using an event-driven and multi-threaded model that is designed to scale. It features an exceptionally light code base, a simple API, decent HTTP protocol handling, keep-alive connections, SSL support (via GNUTLS), HTTP proxy (with keep-alive connection pooling), non-blocking sendfile support (with configurable small file memory cache), cacheable gzip content encoding, cacheable image thumbnails with watermarks (via ImageMagick), a modular design for developers, and the ability to run as a daemon.

WAWAS is a full PHP application server.
The main server core listens to any IP/port and passes data to any mounted protocol on the listener. Implemented protocols are HTTP1.1/1.0, Comet, Telnet, DNS, mail, and FTP. Each protocol runs modules that build response data based on the requests. Memory object persistence allows data and caches to be shared across protocols or time. All configuration uses XML. It can be launched as a daemon, with or without forked workers, and is nearly as fast as Apache in preliminary tests.

Nodetoy is a server that does JSON CRUD, so you can write APPs by writing just HTML and JavaScript. The server has no database, JSON is stored directly on the filesystem. The server responds to AJAX requests containing JSON and follows REST principals. It also contains an HTTP server that supports rewrite and SSI for hosting the HTML pages and static resources.